Electronic devices and systems with remote (wireless) communication functionality are not restricted by signal transmission lines, so such remote communication functionality has become one of the most popular consumer functionalities.
As known by who familiar with related art, a system with remote communication functionality has to transmit communication signals between a transmitter and a receiver in a remote (wireless) fashion. Generally speaking, known prior arts carry the remote communication signals using infra-red (IR) light or electromagnetic waves, such as radio-frequency (RF) or Bluetooth. However, the above prior arts are expensive and thus can not be widely adopted.
On the other hand, ultrasound and/or quasi-ultrasound have been adopted to implement various functionalities, such as ranging (distance estimation) or obstacle detection. However, specific ultrasound actuators or high-frequency oscillators must be adopted for ultrasound transmitting, thus the cost is also expensive.
On the contrary, controllers and/or microprocessors with audio playback and receiving functionality have been widely used with very low cost, so a technique implementing remote communication functionality using ordinary audio receivers and transmitters (e.g., ordinary microphones and speakers) will be very valuable.